Citing earlier work from 2007, they estimated anthrax spores remain viable in the permafrost for 105 years. Buried deeper, the bacteria may be able to hibernate for even longer. At the same time, where meteorological data were available they indicate temperatures in Yakutia are increasing.

“As a consequence of permafrost melting, the vectors of deadly infections of the 18th and 19th centuries may come back,” the scientists warned, “especially near the cemeteries where the victims of these infections were buried.” Cattle grave sites should be monitored, they concluded, and “public health authorities should maintain permanent alertness.”

Romanovsky says the possibility that additional pathogens may be released from the permafrost, if that is indeed the source, makes it even more important to study this specific outbreak closely. Once in the water supply, in theory, a future pathogen could spread outside the local area, carried by people or by migrating birds or animals.

Though the current outbreak is happening during an unusual period of extreme warmth, Romanovsky says that, “if it gets warmer in the future, and it seems like it will, the thawing permafrost could be massive.” A further degradation of the permafrost would allow more opportunity for the emergence of sequestered microbes.